Some tweaks:

Add script.js for theme scripts with 2 jQuery wrappers (immediate and DOM
ready);
Dequeue jquery-migrate.js in functions.php;
Modify colophon in footer.php;
Remove charset meta tag from header.php (server sends proper headers);
Stop WordPress from compressing images in inc/extras.php;
Remove WordPress name and version (generator meta tag) in functions.php;
Add execution time and number of queries in html comment.